The relatively high protein intake required to achieve catch-up growth in LBW infants is not utilized completely unless accompanied by an energy intake that results in excessive fat disposition. We, propose to evaluate a strategy to enhance protein accretion without excessive fat accretion. Specifically, we will evaluate effects of a high- carbohydrate vs an isocaloric high-fat diet on growth, protein utilization and cardiorespiratory function in LBW infants.